"The committee has never before held nominations hearings while the Senate is in recess before an election," the letter stated. "The handful of nominations hearings that have been held during a recess have been with the minority's consent, which is not the case here — in fact, we were not even consulted."

The two hearings are set for Wednesday and Oct. 24. Next week's hearing is tentatively scheduled to include two nominees for appeals judges on the Ninth Circuit, even though Democrats say senators who represent states in the Ninth Circuit would not be able to return to Washington for the hearing.

Democrats want Grassley to delay the hearings until after the Senate returns to Washington on Nov. 13.

"Holding hearings during a recess, when members cannot attend, fails to meet our constitutional advice-and-consent obligations," Democrats wrote in the letter.

Democrats were backed up in their request by progressive outside groups, who warned that Republicans would "abuse their power" by holding a hearing in Washington, D.C., during the recess.

“The Senate is in recess, senators are out of town, every other committee postponed their hearings, but Chairman Grassley still plans to move forward on Trump’s extremist judicial nominees over the objection of the minority party," said Kristine Lucius, executive vice president of policy at The Leadership Conference on Civil and Human Rights.

Lucius added that the recess hearings are an "unprecedented maneuver" and the "latest example of Grassley’s abuse of Senate tradition and Republicans’ relentless attempts to remake the federal courts in Trump’s image."

But Grassley indicated in separate letters to Feinstein and Judiciary Committee Democrats on Monday that he is moving forward with Wednesday's hearing, which he says was initially scheduled for last month.

"You agreed to the October 17 hearing date with full knowledge that the Senate could go into recess before then. And you specifically agreed not to object to the timing of hearings scheduled for October 10, 17, and 24," Grassley wrote in the letter to Feinstein.

He added in the letter to committee Democrats that while they say some of them have conflicts, Feinstein had already agreed to the days.

"The Ranking Member agreed to schedule these hearings for October 17 and 24 before the Senate went into recess. If any conflicts arose after the Senate went into recess, it is up to members to determine how to resolve them," Grassley added.